1. Field of the Invention
The present invention relates to a conductive structure for an electrode assembly of a lithium secondary battery, and more particularly to an electric power collecting and leading structure for an electrode assembly of a lithium secondary battery.
2. Description of the Prior Art
Referring to FIGS. 1 and 2, a spirally coiled electrode assembly 10 of a conventional lithium secondary battery disclosed by U.S. Pat. No. 5,849,431 comprises a web-like positive layer 11, a negative layer 12 and a separator layer 13 that are sequentially laminated to one another and are then wind about a core 14. One side of the positive layer 11 and the negative layer 12 are cut into rectangular teeth that serve as rectangular leads 111 and 131. The rectangular leads 111 and 131 are gathered together and then welded to the outer periphery of the disc-like conductive terminal 15. By such arrangements, the electric power can be outputted out of the electrode assembly 10.
It is to be noted that the respective layers of the electrode assembly are arranged in a concentric manner, and the respective leads are located at different distances to the outer periphery of the conductive terminal. Before welding the respective leads to the conductive terminal, the respective leads must be trimmed and tidied up and then welded to the outer periphery of the conductive terminal.
However, this conventional battery structure still has the following disadvantages:
Firstly, when manufacturing the electrode assembly, it must be careful to avoid the complicated cutting and trimming operation, since the trimming operation will produce bits of waste. If the bits of waste are adhered to the surface of the positive and negative electrode layers, it will lead to an unrecoverable conduction disturbance of the electrode assembly. And in this conventional lithium secondary battery structure, the electrode assembly should be subjected to the teeth cutting operation, this will not only increase the manufacturing difficulties, reducing the acceptance ratio of the products, but will produce bits of waste.
Secondly, the leads of the respective layers of the electrode assembly are arranged in a concentric manner, and the leads must be equal in length, and the length of the lead that is located far away from the outer periphery of the conductive terminal is regarded as a reference value. Therefore, the excessively long leads must be subjected to a tiding up operation in which the excessively long leads are pressed together. However, this tidying up operation will not only increase the complexity of the manufacturing process, but will have the risk of breaking the leads.
Thirdly, the area of the outer periphery of the disc-like conductive terminal to be welded with the leads are very small, if there are too many leads, the battery manufacturing process will become more complicated and difficult.
Referring to FIG. 3, a conventional lithium secondary battery disclosed by U.S. Pat. No. 6,447,946 is illustrated and comprises a plurality of leads 111a and 131a welded to the end periphery of the electrode assembly 10a, and then the leads 111a and 131a are welded to a frame 161 disposed at a side of the battery terminal 16.
The electrode assemblies in the two abovementioned conventional lithium battery structures are all formed or welded with a plurality of leads, and then the leads serve as a medium to which the battery terminal or the conductive terminal, so as to guide the electric power of the electrode assembly out of the battery. It is to be noted that, for a high capacity battery, the number of leads must be relatively increased as compared to a battery of ordinary capacity. Otherwise, in the battery charge or discharge process, the increase of internal resistance will lead to a substantial decrease in the charge and discharge efficiency, or even worse, a failure of battery charge and discharge. However, as for the conventional structure, the number of the leads is difficult to effectively increase since it is limited by the welding and cutting technology.
It is understood from the above description that the battery with a comparatively great number of leads can effectively reduce the internal resistance and reactance of the battery while improving the capacity thereof. However, for such a great number of leads, the welding operation is not only laborsome, but the manufacturing process is complex.
Therefore, the present invention is emphasized on designing such a battery structure whose electrode assembly is in direct electrical contact with the battery terminal without the use of welding operation. On the other hand, via structural design, the electrode assembly is allowed to be in a large area of electrical contact with the battery terminal. In this way, the internal resistance of the battery is substantially reduced while the capacity is improved.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.